Question

Three point charges are fixed as shown in above figure. Find out the electrostatic force felt by the positive charge at the left end of the line?

• A. $\frac{k{Q}^2}{2R^2}$
• B. $\frac{k{Q}^2}{R^2}$
• C. $\frac{3k{Q}^2}{4R^2}$
• D. $\frac{5k{Q}^2}{4R^2}$
• E. $\frac{3k{Q}^2}{2R^2}$

Answer 1

Answer: (C)

$\frac{3k{Q}^2}{4R^2}$

The electrostatic force on charge Q to the left $=$ electric force due to Q at center $+$ electric force due to -Q to the right

or $F=\frac{KQQ}{R^2}+\frac{KQ(-Q)}{(2R{)}^2}=\frac{3K{Q}^2}{4R^2}$